To mount an integrated circuit ("IC ") on a predetermined position on a circuit board, it is necessary to set an exact position of the IC. In order to measure the exact position of the IC, it is necessary to locate the center of the IC and measure its angle of inclination. In the case extracting information regarding the center of the IC and its angle of the inclination using image processing methods, the extraction process is applied to a binarized image in order to make the processing speed high. However, the binarized image is easily damaged by a change in the degree of brightness of lights illuminating the IC, and such methods have trouble measuring exact position .